1. Field of the Invention
The present invention relates to a rocker joint pin for used in a chain to articulately interconnect link plates of the chain, and a method of and an apparatus for producing the rocker joint pin.
2. Description of the Related Art
A chain is constituted by a large number of link plates articulately connected together in an endless fashion by means of connecting pins. The connecting pins are generally classified into two types, one being a round pivot pin and the other being a rocker joint pin. The rocker joint pin is used in many case for silent chains and also for chain belts of continuous variable transmissions (CVTs).
Conventionally, in the manufacture of a connecting pin, a continuous wire drawn in a cross-sectional shape substantially the same as that of a finished connecting pin is cut off or severed into pin stocks of product length. The pin stocks are then subjected to chamfering to form a beveled edge at both longitudinal end faces of each individual pin stock. The chamfering is effected to ensure that the connecting pins can be smoothly inserted into pin-accommodating holes in the link plates during the process of assembling the chain. The chamfered pin stocks are heat treated and then finished into a final shape of the pins.
In the case of the round pivot pin, chamfering is generally achieved by way of barrel finishing (tumbling) or pin-heading (forging). In the case of the rocker joint pins, chamfering is generally achieved by way of barrel finishing. A pin-heading (forging) operation or a cutting operation is used sometimes.
The barrel finishing operation used for chamfering the rocker joint pins is disadvantageous due to a difficulty in forming a sufficiently large chamfered or beveled edge. An attempt to produce a sufficiently large beveled edge by the barrel finishing requires a considerably long processing time, tending to cause undesired removal of material from a different part of the rocker joint pin, such as a convexly arcuate surface. The thus finished rocker joint pin no longer possesses the original cross-sectional shape.
The pin-heading (forging) process used for chamfering the rocker joint pins is also disadvantageous in that, due to a change in the cross-sectional shape of the rocker joint pin, an accurate pin-heading operation is difficult to achieve.
In the case where the pin-heading (forging) operation or the cutting operation is carried out to chamfer the rocker joint pins of a product length, a parts feeder or the like orienting machine must be provided to arrange the individual rocker joint pins into a desired orientation before the pins are processed or chamfered by a pin-heading machine or a cutting machine. This requirement increases the equipment cost, leading to an increase in the manufacturing cost of the rocker joint pins.
It is, accordingly, a general object of the present invention to overcome the problems associated with the conventonal chamfering processes used for forming a beveled edge at both longitudinal end faces of a rocker joint pin.
A more specific object of the present invention is to provide a rocker joint pin for chains, which can be manufactured at a relatively low cost and smoothly assembled with link plates of a chain.
Another object of the present invention is to provide a method which is capable of economically producing a rocker joint pin having a sufficiently large beveled edge at opposite end faces of the pin.
A further object of the present invention is to provide an apparatus for reducing the method into practice.
A still further object of the present invention is to provide a rocker joint pin produced by the foregoing method.
According to one aspect of the present invention, there is provided a rocker joint pin for use in a chain to articulately interconnect link plates of the chain, the rocker joint pin having a beveled edge formed at opposite end faces thereof, the beveled edge having been subjected to grooving to form a V-shaped groove transversely across a surface of a continuous wire, and the end faces having been subjected to cutting to sever the wire at the bottom of the V-shaped groove.
According to another aspect of the present invention, there is provided a method of producing a rocker joint pin for a chain, the pin having a beveled edge at opposite end faces thereof, the method comprising the steps of: intermittently feeding a continuous wire longitudinally along a path; forming a V-shaped groove transversely across a surface of the wire while the wire is at rest; and cutting the wire at the bottom of the V-shaped groove while the wire is at rest, thereby producing a rocker joint pin having a beveled edge at opposite end faces thereof.
The forming step may be achieved either by reciprocating a groove forming punch in a direction perpendicular to the path, or alternatively by reciprocating a cutting tool in a direction orthogonal to the path. The groove forming punch and the cutting tool have a V-shaped cutting edge.
According to still another aspect of the present invention, there is provided an apparatus for producing a rocker joint pin for a chain, the rocker joint pin having a beveled edge at opposite end faces thereof, the apparatus comprising: a feed unit for intermittently feeding a continuous wire longitudinally along a path; a grooving unit disposed downstream of the feed unit for forming a V-shaped groove transversely across a surface of the wire while the wire is at rest; and a cutting unit disposed downstream of the grooving unit for severing the wire at the bottom of the V-shaped groove while the wire is at rest, thereby producing a rocker joint pin having a beveled edge at opposite end faces thereof.
The apparatus may further comprise a positioning unit disposed downstream of the cutting unit for positioning a leading end of the wire.
In one preferred form, the grooving unit comprises a fixed die disposed on one side of the path for supporting one surface of the wire, and a movable grooving punch disposed on the opposite side of the path and reciprocally movable toward and away from the fixed die for forming the V-shaped groove on the opposite surface of the wire, the grooving punch having a V-shaped cutting edge. Preferably, the fixed die has a guide surface so profiled as to comport with a profile of the one surface of the wire, and the cutting edge of the movable grooving punch has a profile complementary in shape to a profile of the opposite surface of the wire.
As a first alternative, the grooving unit may comprise a cooperating pair of aligned, movable grooving punches disposed on opposite sides of the path and reciprocally movable toward and away from each other for forming the V-shaped groove on opposite surfaces of the wire, the grooving punches having a V-shaped cutting edge. It is preferable that the cutting edge of one of the pair of movable grooving punches has a profile complementary in shape to a profile of one of the opposite surfaces of the wire, and the cutting edge of the other of the pair of movable grooving punches has a profile complementary in shape to a profile of the other of the opposite surfaces of the wire.
As a second alterative, the grooving unit may comprise a cutting tool disposed on one side of the path and movable transversely across the path for forming the V-shaped groove on one surface of the wire, the cutting tool having a V-shaped cutting edge. The grooving unit may further comprise a second cutting tool disposed in alignment with the cutting tool and movable transversely across the path for forming the V-shaped groove on the opposite surface of the wire, the second cutting tool having a V-shaped cutting edge.
In one preferred form, the cutting unit comprises a fixed cutting die having a guide hole aligned with the path for the passage therethrough of the wire, and a movable cutting die having a guide hole normally disposed in alignment with the path for the passage therethrough of the wire. The movable cutting die is movable relative to the fixed die between a first position in which the guide hole in the fixed cutting die and the guide hole in the movable cutting die are aligned with each other, and a second position in which the movable cutting die is offset from the path in a direction orthogonal to the path. Preferably, the apparatus further comprises a knockout pin reciprocally movable within the guide hole in the movable cutting die for discharging a rocker joint pin from the movable cutting die while the movable cutting die is disposed in the second position.